System for inspecting and classifying objects such as screws, bolts and the like while in motion

ABSTRACT

Inspection and grading system for threaded objects comprising sequential detection, measurement, and comparison of major and minor diametral values of a threaded object while in motion. Such values are determined along the pitch angle of the threaded object throughout its longitudinal length. Measurements are made cyclically as the object is guided through the detection zone. The measured values are evaluated e.g., by sequential comparison to computer stored values of a standard threaded object and accepted or rejected based on the selective discrimination level. The objects are counted and classified.

llnited States Patent Bornemeier 51 Mar. 21, 1972 SYSTEM FOR INSPECTINGAND CLASSIFYING OBJECTS SUCH AS SCREWS, BOLTS AND THE LIKE WHILE INMOTION Inventor: Dwight D. Bornemeier, Ann Arbor, Mich.

Assignee: Sensors, Inc.

Filed: Nov. 19, 1970 Appl. No.: 90,886

1m. (:1 ..B0' 7c 5 00 Field of Search ..209 80, 82, 1 1 1.7; 365 165,365/168; 250/223 References Cited UNITED STATES PATENTS I-Iomoch ,'Z 09/8 2 X 3,395,794 8/1968 Petry 209/82 X Primary ExaminerAllen N. KnowlesAssistant Examiner-Gene A. Church AttorneyShanley and ONeil Inspectionand grading system for threaded objects comprising sequential detection,measurement, and comparison of major and minor diametral values of athreaded object while in motion. Such values are determined along thepitch angle of the threaded object throughout its longitudinal length.Measurements are made cyclically as the object is guided through thedetection zone. The measured values are evaluated e.g., by sequentialcomparison to computer stored values of a standard threaded object andaccepted or rejected based on the selective discrimination level. Theobjects are counted and classified.

ABSTRACT 12 Claims, 3 Drawing Figures Patented March 21, 1972 I 73,650,397

2 Sheets-Sheet 1 56 DATA L 30 r PROCESSlNG UNIT INVENTOR DWIGHT D.BORNEMEIER Patented Min-ch 21, 1972 I 2 Sheets-Sheet 2 I sET COUNTERSsTART CYCLE MEASUREMENT b YEs LAST COUNTER INDEXED 76 a as N0 W I MINTAA R Ys 0R J0 i LAST INDEX COUNTER STOP MINO INDEXED T 1 COUNTER j YESNO MINOR MAJOR l INDEX M O READ MINOR COUNTER REGISTER- GREATER THANSELECTED mmmm? NO YES READ MAJOR COUNTER REJECT AL N0 GREATER THAN PARTsEEEcTEo mmmum I YES I SYSTEM FOR INSPECTING AND CLASSIFYING OBJECTSSUCH AS SCREWS, BOLTS AND THE LIKE WHILE IN MOTION This invention isconcerned with methods and apparatus for inspecting and grading objectshaving undulating dimensions such as screws, bolts, studs, and the like,at high speeds and without requiring mechanical contact with suchobjects. In its more specific aspects the invention is concerned withmethods and apparatus for automatic inspection and grading of threadedobjects while in motion, for example as part of production lineprocessing.

Many threaded objects, for example those for automotive and electroniccontrol uses, require precision inspection. The highest level inspectionprovided in the prior art has been limited to manual operation based oncomparison viewing. Apparatus for static inspection of threaded objectsare shown in U.S. patents to Banfield U.S. Pat. No. 1,421,057 and toCooke U.S. Pat. No. 1,424,556.

While there has been more recent development of measuring apparatus,e.g., apparatus for measurement of the area of an object as covered inthe Hatcher Jr. et a1. U.S. Pat. No. 3,515,487, or length and widthmeasurements for purposes of grading of objects as shown in the patentto Rock Jr. U.S. Pat. No. 3,480,141, or measurements for componentsizing or selection as shown in the patents to Petry U.S. Pat. No.3,395,794 and Schnieder U.S. Pat. No. 3,248,845, and various teachingson use of T.V. comparators as shown in the patents to Rosin et al. U.S.Pat. No. 3,178,510 and Reed U.S. Pat. No. 3,218,389, none of these priordevelopments has discovered or utilized the basic concept of the presentinvention. Measurement of surface undulations of an object, while theobject is in motion, is novel in the art.

The present invention provides for automatic, uniform, inspection ofnon-stationary objects, and is characterized by an electro-opticalsystem which replaces inspection and decision functions of an operator.A distinct advantage of the invention is that it allows an object to bein motion, within given constraints, during inspection so thatproduction is not halted for inspection. Other advantages include rapidreadout and detection of sub-standard parts, provision for predeterminedcategorization of defects which are cause for rejection, provision forinstantaneous records of parts rejected in each category and the totalnumber processed, and provision for setting of discrimination level sothat parts failing a given number of tolerance requirements can beaccepted, if desired.

Other objects and advantages of the invention will be considered inpresenting a specific embodiment of the invention represented in theaccompanying drawings. In such drawings:

FIG. 1 is a schematic perspective presentation of a system embodying theinvention,

FIG. 2 is a detailed cross sectional view of a portion of a threadedobject and a schematic presentation of detector apparatus embodying theinvention,

FIG. 3 is a box diagram schematic presentation for illustratingfunctions carried out by the invention.

The invention teaches use of a shadow image of an elevational view of athreaded object. Magnification of the image by a coordinated opticalsystem is utilized to increase resolution and accuracy. The shadow imageis projected onto detector means including a preselected arrangement ofa series of individual detector elements positioned to provide highresolution and accuracy. The undulating character of objects beinginspected, such as threaded objects, is taken into consideration by asignificant contribution of the invention in which detector means arecyclically operated to permit measurement of major and minor diametersand other thread characteristics while the object is in motion. Cyclicsequential comparison of measured values and stored values for astandard model can be made for classification purposes or otherwise,e.g., by setting a minimum number of major and minor diameter values tobe established before acceptance.

Referring to FIG. 1, a light source projects a beam of light 12 towardbeam optic expander structure including lens 14 and 16. The expandedbeam 18 is projected from mirror 20 toward mirror 22 as shown. Suitablelight energies include optical wave length, electromagnetic radiationincluding visible light, monochromatic light including infra-red andultraviolet, and light energy in the quasi-optical field.

In general, for operation of the invention with opaque or semi-opaqueobjects, where the concern is with configuration faults, the wave energyused should be largely non-penetrative in character. For example,infra-red although considered under some circumstances to be slightlypenetrative would be operable while a wave energy such as X-rays wouldnot be suitable for determining accurately the dimensional characteristics of the outline of a threaded object. In brief, suitable waveenergy for the present invention should not diminish resolution; thewavelength should not be too short so as to cause undue penetration nor,too long so as to cause fuzzy edging in shadov. imaging.

In FIG. 1, the light energy from mirror 20 is directed toward mirror 22through an image system lens 24. Such light energy path may include anobject plane for viewing. Other systems for creating a shadow image ofan object under inspection may be used without departing from the scopeof the invention.

Part of the invention is control of an object's passage through theobject plane. An object can be projected or travel under free fallingconditions through the object plane. Velocity and orientation can becontrolled in a predetermined manner and are held within practicallimits relative to the equipment being used. Guide means 30 guide theobject 26 in a direction to permit elevational view inspection duringits passage through the object plane; such guide means usually take theform of suitable transparent structure which will not significantlyalter the optical requirements.

After passage through the object plane, object 26 is directed to chute32 having a plurality of outlets, such as 34 and 36, with a selectorvane 38 controlling the disposition of the object.

Considering further the image system of FIG. 1, the magnified image ofthe object 26 while in the object plane is projected from mirror 22 inthe form of beam 40 toward detector means 44.

Detector means 44 are electrically coupled over lines 48 and 50 to adata processing unit 54. Line 56 electrically connects data processingunit 54 to the selector vane 38.

As shown in FIG. 1, in addition to a plurality of aligned detectors, thedetecting means include a start detector 60 and a stop detector 62. Thestart detector 60 initiates the sequential cyclic interrogation of thepart and stop detector 62 signals passage of the object. Such start andstop detectors are located along the centerline, that is thelongitudinal axis of the image; but can be otherwise located as requiredto provide the necessary initiation and termination of interrogation.

The image projected on the detector means 44 is a magnified shadowoutline of the object as shown in FIG. 2. That is, an elevational view,in magnified form, is projected on a plurality of individual detectorelements, such as 64, aligned in closely spaced juxtaposition along aline which, in the present instance, is coincident with the pitch angleof the threaded object. This alignment is transverse to the surfaceundulations of the object so as to permit accurate measurement of thescrew thread diameter at any instant.

As shown, the edges of the object determine the boundary of illuminatedand non-illuminated areas in the image plane. Dimensional measurement ofthe shadow image is provided. The photo-responsive detector elements,such as 64, are arranged in array with center-to-center spacing of aslow as 0.002 inch. Considering a magnification from the image system often a resolution of 0.0002 inch is provided.

The measurement of the major and minor diameters, or intermediate valuesis accomplished by electrically reading the state of each photo-detectorelement of which 64 is an example. Such detector elements can beelectrically read either sequentially or in parallel and can be wired torespond conductively or non-conductively to irradiation. The object 26may be moved through the object plane at velocities on the order ofmeters per second without diminishing the inspection resolution becauseof the rapidity of interrogation. Operation teachings of the inventionthe speed of the part, as projected or under free fall conditions, canbe at the rate of a meter per second, for example, or greater dependingon the speed of the electronic interrogation of the detector meansselected. With the values of the specific embodiment presented it isseen that such speed of movement for the part would not introduce anymeasurable error. At increased speeds the interrogation would berequired to be faster, however any normal production operation could behandled within the readily available values set forth above.

The relative motion between the detectors and the part is taken care ofby the cyclic reading. Also, it is to be noted that this relative motionplays an important part in the invention in permitting the entire partto be scanned, by repeated measurements across the part, each tomicrosecond cycle time or less. Therefore each thread can be inspectednot only for major and minor diameters but sufficiently frequently toestablish slope.

With objects having spaced series of threads or requiring nonuniformthreads, cycling time can be adjusted to the particular sequence, ifrequired. But, in general, comparing the values read to standard valuesin a data processing unit will take care of any practical productionsituation.

Data processing in the case of screw threads can be accomplished bycomparing the measurement obtained each cycle with standard values forthe thread which are stored in the electronic memory unit of the dataprocessor. Detection of a predetermined number of major and minordiameter values can be relied on solely for grading. The axis of thebolt or screw to be inspected is aligned in proper relationship to thedetector units so that diametral values can be readily and accuragelydetermined; ordinarily about 5 angled relationship between thelongitudinal axis of the object and the centerline between the detectorcan be tolerated without significant effect on accuracy because of theinsignificant linear change, at such small angles, compared to detectorresolution. I

In the specific example of FIG. 2, linear value 66 is selected torepresent a major diameter value which is slightly less than the desiredmajor diameter for the threaded object. 1n other words, value 66 takesinto consideration a tolerance limit for the major diameter.

In the same embodiment, linear value 68 represents a minor diametervalue which is slightly greater than the desired minor diameter, i.e.,within the allowed tolerance.

These diametral values are entered in the data processing unit. Atypical quality control requirement would be that the threaded objecthave a certain minimum number of major and minor diameter measurements,within the above tolerance limits, along its length. During inspectioneach measurement of a major and minor diameter within the values 66 and68 is counted. The data processor will keep a record of the count of themajor and minor diameters measured and direct the grading of the objecteither during inspection or after full inspection. A lesser number ofmajor or minor diameter values than designated would cause rejection.

With higher quality control requirements the sequence of measurementscan be compared with stored information in the processing unit. It isclear that storing of profile information is, for practical purposes,unlimited so that numerous sequential tests can be performed includingtests not limited to periodic or symmetrical profile outlines. Thenumber of profiles which can be stored in a single unit are in thethousands, and increasing with improved memory storage units, so thatfor practical manufacturing purposes there is no limit placed on theoperation by the data processing unit. The most complex requirementsincluding thread slope, tapered threads or shanks, apertured shanks,minimum head dimensions, and the like, can be handled.

In making a measurement of a major and minor diameter the photo detectorarrays can be read in a'number of ways. After start of the cyclicinterrogation of the detector arrays by start detector 60, measurementscan be made at cyclic intervals corresponding to the major and minordiameters positioning of the threaded object. In a more simplifiedarrangement, diametral measurements are made continuously and major andminor diameters sensed by detected values above and below the presenttolerance levels.

Positioning of the detector unit is accurately known, as is theintermediate spacing between the detector units. Hence the measuredlinear values 70 and 72 are readily determined electronically and thecenterline value 74 is accurately known. A summation value 76 ofcenterline value 74 and the measured linear values 70 and 72 provides ameasurement near the major diameter in the example as shown in FIG. 2.

Similar measurements continue throughout the length of the part. Faultsare recorded in the data processing unit and faults beyond apredetermined discriminator level determine whether the part should beejected or maintained. The signal from the data processing unitpositions the selector vane 38 and controls disposition of the threadedobject.

Measurements can be made obtaining differing elevational views of theobject from varying angled relationships by making measurements from aplurality of stations. Also the object being inspected can be rotatedduring viewing. From a practical viewpoint such added viewing is notrequired on threaded objects produced by standard manufacturingprocesses in use today since a thread fault will rarely be limited to asingle profile with such manufacturing processes.

In a typical sequential measurement arrangement of a threaded object,the data processing unit will include at least two counters, one formajor diameters and one for minor diameters. The minimum number ofmeasurable major diameters and minor diameters for an acceptable partwill be set in the data processing unit. Such values can be indicated bythe data processing unit along with measured values as made.

During inspection, each measurement made in the manner indicated by FIG.2 is compared with the major diameter value 66 (with tolerance) and theminor diameter value 68 (with tolerance). The first time a majordiameter is measured the counter for the major diameter is indexed. Thefirst time a measurement of the minor diameter occurs, the counter forthe minor diameter is indexed. These counters can be set up as shown inthe data processing flow chart of FIG. 3 so as to be indexed only ifalternate major ad minor diameter measurements occur. That is, the majordiameter counter will be indexed again only if the minor diametercounter is indexed intermediately. After the part has passed through theinspection area it no longer produces an image on the detectors. Thenthe number of counts in each counter is compared with the selected valuefor the major and minor diameter values. If the number of major andminor diameters counted exceed the minimum required for each, then thepart is accepted. Variations in this data processing scheme can be madeby comparing a sequence of measurements sequentially with storedinformation in the data processing unit.

As shown in the flow chart for the data processing unit, FIG. 3, cyclingis started by an object passing start detector 60. Measurement of thevalue 76, that is, the summation of centerline value 74 and the measuredvalues of each bank 70 and 72 are made. This measurement value isinterrogated to determine whether the summation value 76 is greater thanor equal to the minor diameter value. When the summation value 76 isgreater than the minor diameter value 68, the measurement isinterrogated to determine whether it is equal to or greater than themajor diameter value 66. If the answer to this latter interrogation isno, another measurement is called for. Measurements and interrogationscontinue; when the summation value 76 is equal to or greater than themajor diameter value 66 then, the counter for the major diameter isindexed, that is increased by one. The cycle is repeated with the minordiameter counter being indexed when the summation value 76 readingsindicate a measurement of a minor diameter.

After final inspection the minor diameter counter is read to determinewhether the minor diameters counted were greater than the selectedminimum. If not, the part is rejected. Similarly, the major diametercounter is read and if the value there is not greater there than theselected minimum the part is rejected. Otherwise, if both values, i.e.,major and minor diameter counter values, exceed the minimum selected thepart is accepted.

Other data processing and indexing approaches are readily available tothose skilled in the art and the flow chart shown in FIG. 3 isrepresentative only of a simplified measuring system in which continuousmeasurements are taken. With a standardized item, traveling at astandardized speed and orientation, the cyclic measurements could betimed to the major and minor diameter locations after initial start upand, the part could be accepted immediately after the minimum number ofmajor and minor diameters for an acceptable part are reached.

In addition, other imaging systems can be utilized without departingfrom the spirit of the invention so that in determining the scope of theinvention reference should be had to the appended claims.

What is claimed is:

1. An electro-optical system for in-line inspection of of opaque andsemi-opaque light attenuating objects having an undulating surface suchas bolts, screws, studs, and the like, while traveling in an axialdirection transverse to a sectional view of such undulating surfacecomprising source means for radiant energy which is substantiallynonpenetrative in character,

optic means for establishing an image system with an object plane forelevational viewing of such objects while traveling through the objectplane,

guide means for directing such objects along a predetermined path intothe object plane and providing a predetermined orientation for suchobjects,

detector means positioned to receive a projection of an object beinginspected during passage through the object plane, the detector meansincluding a plurality of individual detector elements arranged inside-by-side predetermined spaced relationship to detect dimensionalcharacteristics from a shadow image of the object cast on the detectorelements during passage of the object through the object plane,

meansfor cyclically interrogating the individual detector elements tosequentially measure dimensional characteristics of the undulatingsurface during such passage, and

data processing means responsive to such cyclic interrogation forgenerating a signal to control disposition of the object.

2. The system of claim 1 in which the data processing means includestorage means for storing dimensional values ofa standard model of theobject under inspection and including means for comparing thesequentially measured dimensional values for such object with the storeddimensional values for a standard model of the object to determineclassification of the inspected object.

3. The system of claim 1 in which the detector means are in uniformlyspaced relation.

4. The system of claim 1 in which the optic means magnify the image ofthe object during inspection and as cast on the detector means.

5. The system of claim 1 for inspecting an elongated threaded object inwhich the plurality of detector elements are arranged in side-by-siderelation along a line which coincident with the pitch angle of thethreaded object and transverse to its longitudinal axis.

6. The system of claim 5 in which spacing between center points of thedetector elements along a line coincident with the pitch angle is about0.002 inch to about 0.02 inch.

7. The system of claim 1 in which the detector elements comprisephoto-responsive semi-conductor cells electrically coupled to produce aninput signal for the data processing means.

8. The system of claim 1 in which the data processing means includes acounter means for ascertaining and recording the number of threadedobjects inspected.

9. The system of claim 1 further including ejector means connected to beactivated by the computer means to eject parts having a predeterminednumber of faults.

10. The system of claim 1 in which the guide means defines a tubularconfiguration for the object to be inspected and comprises materialwhich is substantially transparent and nonattenuating to the radiantenergy.

1 l. A method for electro-optically inspecting light attenuating objectshaving an undulating surface, such as bolts, screws, studs, and thelike, comprising establishing an object viewing plane for projecting amagnified image of an object to be inspected,

guiding an object to be inspected along a predetermined path and withpredetermined orientation through the object plane so as to have itsundulating surface cast a shadow image on a plurality of detectorsaligned in predetermined spaced relationship along a line transverse tosuch undulating surface shadow image,

cyclically interrogating the detector means to sequentially measurediametral characteristics of the undulating surface and generatingresponsive signals,

directing signals form the detector means to a data processing means,and

controlling classification of the object being inspected responsively tosuch sequentially measured diametral characteristic.

12. The method of claim 11 including the step of comparing diametralcharacteristics of the undulating surface as detected by the detectormeans to standard values for such surfaces stored in the data processingmeans.

1. An electro-optical system for in-line inspection of of opaque andsemi-opaque light attenuating objects having an undulating surface suchas bolts, screws, studs, and the like, while traveling in an axialdirection transverse to a sectional view of such undulating surfacecomprising source means for radiant energy which is substantiallynonpenetrative in character, optic means for establishing an imagesystem with an object plane for elevational viewing of such objectswhile traveling through the object plane, guiDe means for directing suchobjects along a predetermined path into the object plane and providing apredetermined orientation for such objects, detector means positioned toreceive a projection of an object being inspected during passage throughthe object plane, the detector means including a plurality of individualdetector elements arranged in side-by-side predetermined spacedrelationship to detect dimensional characteristics from a shadow imageof the object cast on the detector elements during passage of the objectthrough the object plane, means for cyclically interrogating theindividual detector elements to sequentially measure dimensionalcharacteristics of the undulating surface during such passage, and dataprocessing means responsive to such cyclic interrogation for generatinga signal to control disposition of the object.
 2. The system of claim 1in which the data processing means include storage means for storingdimensional values of a standard model of the object under inspectionand including means for comparing the sequentially measured dimensionalvalues for such object with the stored dimensional values for a standardmodel of the object to determine classification of the inspected object.3. The system of claim 1 in which the detector means are in uniformlyspaced relation.
 4. The system of claim 1 in which the optic meansmagnify the image of the object during inspection and as cast on thedetector means.
 5. The system of claim 1 for inspecting an elongatedthreaded object in which the plurality of detector elements are arrangedin side-by-side relation along a line which coincident with the pitchangle of the threaded object and transverse to its longitudinal axis. 6.The system of claim 5 in which spacing between center points of thedetector elements along a line coincident with the pitch angle is about0.002 inch to about 0.02 inch.
 7. The system of claim 1 in which thedetector elements comprise photo-responsive semi-conductor cellselectrically coupled to produce an input signal for the data processingmeans.
 8. The system of claim 1 in which the data processing meansincludes a counter means for ascertaining and recording the number ofthreaded objects inspected.
 9. The system of claim 1 further includingejector means connected to be activated by the computer means to ejectparts having a predetermined number of faults.
 10. The system of claim 1in which the guide means defines a tubular configuration for the objectto be inspected and comprises material which is substantiallytransparent and non-attenuating to the radiant energy.
 11. A method forelectro-optically inspecting light attenuating objects having anundulating surface, such as bolts, screws, studs, and the like,comprising establishing an object viewing plane for projecting amagnified image of an object to be inspected, guiding an object to beinspected along a predetermined path and with predetermined orientationthrough the object plane so as to have its undulating surface cast ashadow image on a plurality of detectors aligned in predetermined spacedrelationship along a line transverse to such undulating surface shadowimage, cyclically interrogating the detector means to sequentiallymeasure diametral characteristics of the undulating surface andgenerating responsive signals, directing signals form the detector meansto a data processing means, and controlling classification of the objectbeing inspected responsively to such sequentially measured diametralcharacteristic.
 12. The method of claim 11 including the step ofcomparing diametral characteristics of the undulating surface asdetected by the detector means to standard values for such surfacesstored in the data processing means.